What is the effect of Bickerstaff encephalitis on reflexes and how is it treated?

Bickerstaff Brainstem Encephalitis: Reflex Abnormalities and Treatment

In Bickerstaff brainstem encephalitis (BBE), areflexia (absent tendon reflexes) is a characteristic feature that occurs alongside ophthalmoplegia and ataxia, and treatment typically consists of intravenous immunoglobulin (0.4 g/kg daily for 5 days) or plasma exchange (200-250 ml/kg for 5 sessions). 1

Clinical Features and Reflex Abnormalities

• BBE is considered part of the Guillain-Barré syndrome (GBS) spectrum, sharing clinical and pathophysiological features with GBS and Miller Fisher syndrome (MFS) 1
• The classic triad of symptoms in BBE includes:
  • Ophthalmoplegia (eye movement abnormalities)
  • Ataxia (coordination problems)
  • Altered consciousness (distinguishing it from MFS) 1, 2
• Areflexia (absent tendon reflexes) is a hallmark feature of BBE, occurring at some point during the clinical course 1, 3
• Unlike typical GBS, BBE patients may develop signs of brainstem dysfunction including impaired consciousness and pyramidal tract signs 1, 4
• Facial diplegia and hemisensory loss may also be present in some cases 2

Pathophysiology of Reflex Abnormalities

• BBE is considered an autoimmune disorder mediated by anti-GQ1b IgG antibodies, which are present in approximately 75% of cases 5
• These antibodies can affect both peripheral and central nervous systems, explaining the mixed clinical picture 2, 3
• Electrophysiological studies in BBE patients may show:
  • Peripheral abnormalities: absent F-waves and H-reflexes
  • Central abnormalities: absent cortical responses with normal peripheral responses 2
• The areflexia in BBE likely results from involvement of peripheral nerves and nerve roots, similar to GBS 3

Diagnostic Approach

• Diagnosis is primarily clinical, based on the triad of ophthalmoplegia, ataxia, and altered consciousness 3, 4
• Key diagnostic tests include:
  • Anti-GQ1b IgG antibody testing (positive in 75% of cases) 5
  • MRI of the brain (may show abnormalities in the brainstem, thalami, and basal ganglia in some cases) 6
  • CSF analysis (may show inflammatory changes) 5
  • Electrophysiological studies (to demonstrate peripheral and central involvement) 2
• BBE must be differentiated from other causes of encephalitis and brainstem dysfunction 1

Treatment Recommendations

• First-line treatments for BBE include:
  • Intravenous immunoglobulin (IVIG) at 0.4 g/kg daily for 5 days 1
  • Plasma exchange (200-250 ml/kg for 5 sessions) as an alternative to IVIG 1
• High-dose corticosteroids may be considered, especially in cases with features of Acute Disseminated Encephalomyelitis (ADEM) 7, 8
• Supportive care is essential, particularly for patients with:
  • Decreased level of consciousness
  • Respiratory compromise
  • Autonomic dysfunction 8
• Patients should be managed in appropriate settings including neurological wards, high dependency units, or intensive care units depending on severity 8

Prognosis and Follow-up

• Most typical BBE cases with positive anti-GQ1b antibodies show good recovery 5
• Atypical BBE cases (negative anti-GQ1b antibodies, marked CSF pleocytosis, abnormal brain MRI) may have longer recovery times and residual deficits 5
• Recovery can continue for more than 3 years after onset 1
• Recurrence is rare (2-5%), but has been reported, including fatal outcomes in pediatric cases 1, 6
• All patients should have access to assessment for rehabilitation, as sequelae may not be immediately apparent at discharge 8

Pitfalls and Caveats

• BBE can be misdiagnosed as other forms of encephalitis or brainstem lesions 1
• The presence of normal or even exaggerated reflexes does not exclude BBE, especially early in the course 1
• Behavioral changes can be mistaken for primary psychiatric illness, leading to delays in diagnosis and appropriate treatment 9
• Patients should not be discharged without either a definite diagnosis or a clear follow-up plan 8
• In severe cases, BBE can progress to respiratory failure or even brain death, requiring prompt recognition and treatment 6